1. Field of the Invention
The present invention relates to error detecting, and more particularly relates to an error detecting methodology for a moving image transmitting system.
2. Background of Related Art
A moving image transmitting system may include a transmitting side and a receiving side that are coupled together by a channel. The channel may have a limited capacity in which to transmit information based on restricting conditions such as a band limit (or bandwidth) characteristics and/or background noise. When information is transmitted that exceeds a limit of the channel, there is a high probability that the receiving side may misjudge the information or even fail to receive all the information.
Channel coding may be used in view of those problems. One purpose of channel coding is to transmit as much information as possible. Another purpose of channel coding is to transmit information with as little error as possible. However, these two purposes of channel coding may be contradictory to each other.
Coding may involve converting an analogue signal into a data signal (or a digital signal). This may also be referred to as source coding. Channel coding is coding data that has undergone the source coding into another form. Channel coding may include an entropy coding, an error control coding, and an encryption, for example. These three types of coding will now be briefly discussed.
Entropy coding may reduce the number of data bits (i.e., data length) by compressing data so that the data can be transmitted as much as possible through a channel having a limited capacity. This technique for compressing data at the time of transmitting the image signal may be greatly utilized especially when an image signal has a large amount information (or data length).
Error control coding may involve coding source coded data into data of another form at the transmitting side. This may be done so that the receiving side can detect error bits and correct the data if an error is generated at an arbitrary bit at the time of data transmission. At this time, the source coded data is referred to as an information word, and the channel coded data is referred to as a code word. Transmission data between the receiving side and the transmitting side may include the information word and the code word. In order to control a transmission error, a transmitter (or the transmitting side) may transmit data including a redundancy bit added to an information bit. The receiving side may detect error bits of the received data using the redundancy bit and corrects the data. Error control coding may differ from entropy coding in that error control coding may increase an amount of data that is being transmitted.
Encryption is a technique for preventing information from being invaded without permission from outside, or from being arbitrarily fabricated. Transmission data between the transmitter and the receiver may include bits having no meaning (i.e., meaningless bits) such as a byte alignment code as well as meaningful bits such as the information word (or information bits) and the code word (or code bits).
FIG. 1 is an exemplary view of transmission data including a byte alignment code. Byte alignment may add several codes to a transmission data block so that the transmission data block can have a size relative to a number of byte units (i.e., a multiple of eight). For example, if a size of the transmission data block is 140 bits, then four ‘0’ bit codes may be added to an end of the transmission data block. As another example, if a size of the transmission data block is 161 bits, then seven ‘0’ bit codes may be added to an end of the transmission data block.
In video coding, a starting bit of a starting code is associated with a boundary of a byte in order to easily search for the starting code. The byte alignment code may be inserted into each block (or frame) of the transmission data. In some circumstances, a data block can exist without having any byte alignment code. If a size of the data block is a multiple of eight, then a corresponding data block may not have a byte alignment code.
In background art, a channel code may be transmitted in order to improve error detection efficiency. However, the amount of transmission data may increase. Additionally, since 24˜30 minimum unit images (i.e., stationary images) may be transmitted per second for moving image data, the byte alignment code may lower the data transmission efficiency.